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    <title>Document</title>
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    <script>
        function fn(n){
            if(n==1){
                return 1;
            }
            return n+fn(n-1);
        }
        console.log(fn(100));
        console.log("---------");




        function fn2(n){
            console.log("hello world!");
            if(n==1){
                return;
            }
            return fn2(--n);
        }
        fn2(10);
    </script>
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